Method for Dicing Die Attach Film

ABSTRACT

The present invention provides a method for dicing a substrate on a composite film. A work piece having a support film, a frame and a substrate is provided. The substrate has a top surface and a bottom surface. The top surface of the substrate has at least one die region and at least one street region. The composite film is interposed between the substrate and the support film. Substrate material is etched from the at least one street region to expose a portion of the composite film using a substrate etch process. A first component of the composite film is etched using a first etch process. A second component of the exposed portion of the composite film is plasma etched using a second etch process.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority from and is related to commonly ownedU.S. Provisional Patent Application Ser. No. 62/680,145 filed Jun. 4,2018, entitled: METHOD FOR DICING DIE ATTACH FILM and U.S. ProvisionalPatent Application Ser. No. 62/721,380 filed Aug. 22, 2018, entitled:METHOD FOR DICING DIE ATTACH FILM, these Provisional Patent Applicationsincorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to the use of an apparatus for the formation ofindividual device chips from a semi-conductor wafer and a die attachfilm.

BACKGROUND

Semi-conductor devices are fabricated on substrates which are in theform of thin wafers. Silicon is commonly used as the substrate material,but other materials, such as III-V compounds (for example GaAs and InP)are also used. In some instances (for example, the manufacture of LED's)the substrate can be a sapphire or silicon carbide wafer on which a thinlayer of a semi-conducting material is deposited. The diameter of suchsubstrates range from 2 inches and 3 inches up to 200 mm, 300 mm, and450 mm and many standards exist (e.g., SEMI) to describe such substratesizes.

Plasma etching equipment is used extensively in the processing of thesesubstrates to produce semi-conductor devices. Such equipment typicallyincludes a vacuum chamber fitted with a high density plasma source suchas Inductively Coupled Plasma (ICP) which is used to ensure high etchrates, necessary for cost-effective manufacturing. In order to removethe heat generated during the processing, the substrate is typicallyclamped to a temperature controlled support. A pressurized fluid,typically a gas such as Helium is maintained between the substrate andthe support to provide a thermal conductance path for heat transfer. Amechanical clamping mechanism, in which a downward force is applied tothe top side of the substrate, may be used, though this may causecontamination due to the contact between the clamp and the substrate.Work piece bowing may also occur when using a mechanical clamp, sincecontact is typically made at the edge of the work piece and apressurized fluid exerts a force on the back of the work piece. Morefrequently an electrostatic chuck (ESC) is used to provide the clampingforce.

Numerous gas chemistries appropriate to the material to be etched havebeen developed. These frequently employ a halogen (e.g., Fluorine,Chlorine, Bromine, Iodine, etc.) or halogen-containing gas together withadditional gases added to improve the quality of the etch (for example,etch anisotropy, mask selectivity and etch uniformity). Fluorinecontaining gases, such as SF₆, F₂ or NF₃ are used to etch silicon at ahigh rate. In particular, a process (Bosch or TDM) which alternates ahigh rate silicon etch step with a passivation step to control the etchsidewall, is commonly used to etch deep features into silicon. Chlorineand Bromine containing gases are commonly used to etch III-V materials.

Plasma etching is not limited to semiconducting substrates and devices.The technique may be applied to any substrate type where a suitable gaschemistry to etch the substrate is available. Other substrate types mayinclude carbon containing substrates (including polymeric substrates),ceramic substrates (e.g., AlTiC and sapphire), metal substrates, andglass substrates.

To ensure consistent results, low breakage and ease of operation,robotic wafer handling is typically used in the manufacturing process.Handlers are typically designed to support the wafers with minimalcontact, to minimize possible contamination and reduce the generation ofparticulates. Edge contact alone, or underside contact close to thewafer edge at only a few locations (typically within 3-6 mm of the waferedge) is often employed. Handling schemes, which include wafercassettes, robotic arms and within process chamber fixtures includingthe wafer support and ESC, are designed to handle the standard wafersizes as noted previously.

After fabrication on the substrate, the individual devices (die orchips) are typically separated from each other prior to packaging orbeing employed in other electronic circuitry. For many years, mechanicalmeans have been used to separate the die from each other. Suchmechanical means have included breaking the wafer along scribe linesaligned with the substrate crystal axis or by using a high speed diamondsaw to saw into or through the substrate in a region (streets) betweenthe die. More recently, lasers have also been used to facilitate thescribing and dicing process.

Such mechanical wafer dicing techniques have limitations which affectthe cost effectiveness of this approach. Chipping and breakage along thedie edges can reduce the number of good die produced, and the processbecomes more problematic as wafer thicknesses decrease. The areaconsumed by the saw bade (kerf) may be greater than 100 microns which isvaluable area not useable for die production. For wafers containingsmall die (e.g., individual semiconductor devices with a die size of 500microns by 500 microns) this can represent a loss of greater than 20%.Further, for wafers with many small die and hence numerous streets, thedicing time is increased, and productivity decreased, since each streetis cut consecutively. Mechanical means are also limited to separationalong straight lines and the production of square or oblong shapedchips. This may not represent the underlying device topology (e.g., ahigh power diode can be round) and so the rectilinear die format resultsin significant loss of useable substrate area. Laser dicing also haslimitations by leaving residual material on the die surface or inducingstress into the die.

It is important to note that both sawing and laser dicing techniques areessentially serial operations. Consequently, as device sizes decrease,the time to dice the wafer increases in proportion to the total dicingstreet length on the wafer.

Recently plasma etching techniques have been proposed as a means ofseparating die and overcoming some of these limitations. After devicefabrication, the substrate can be masked with a suitable mask material,leaving open areas between the die. The masked substrate can be thenprocessed using a reactive-gas plasma which etches the substratematerial exposed between the die. The plasma etching of the substratemay proceed partially or completely through the substrate. In the caseof a partial plasma etch, the die can be separated by a subsequentcleaving step, leaving the individual die separated. The techniqueoffers a number of benefits over mechanical dicing:

1) Breakage and chipping is reduced;

2) The kerf dimensions can be reduced to well below 20 microns;

3) Processing time does not increase significantly as the number of dieincreases;

4) Processing time is reduced for thinner wafers; and

5) Die topology is not limited to a rectilinear format.

After device fabrication, but prior to die separation, the substrate maybe thinned by mechanical grinding or similar process down to a thicknessof a few hundred microns, or even less than a hundred microns.

Prior to the dicing process, the substrate is typically mounted on adicing fixture. This fixture is typically comprised of a rigid framethat supports an adhesive support film. The substrate to be diced isadhered to the support film. This fixture holds the separated die forsubsequent downstream operations. Most tools used for wafer dicing (sawsor laser based tools) are designed to handle substrates in thisconfiguration and a number of standard fixtures have been established;however, such fixtures are very different from the substrates which theysupport. Though such fixtures are optimized for use in current waferdicing equipment, they cannot be processed in equipment which has beendesigned to process standard substrates. Thus, current automated plasmaetching equipment is not suitable for processing substrates fixtured fordicing and it is difficult to realize the benefits that plasma etchtechniques should have for die separation.

Some groups have contemplated using plasma to singulate die from wafersubstrates. U.S. Pat. No. 6,642,127 describes a plasma dicing techniquein which the substrate wafer is first attached to a carrier wafer via anadhesive material, before plasma processing in equipment designed forprocessing silicon wafers. This technique proposes adapting the formfactor of the substrate to be diced to be compatible with standard waferprocessing equipment. While this technique allows standard plasmaequipment to dice the wafer, the proposed technique will not becompatible with standard equipment downstream of the dicing operation.Additional steps would be required to either adapt the downstreamequipment or revert the substrate form factor for standard downstreamequipment.

U.S. Patent Application No. 2010/0048001 contemplates the use of a waferadhered to a thin membrane and supported within a frame. However, in the2010/0048001 application, the masking process is achieved by adhering amask material to the backside of the wafer and using a laser to definethe etch streets prior to plasma processing. In contrast to standarddicing techniques which singulate the substrate from the front side,this technique introduces additional complex and expensive steps whichmay negate some of the advantages of plasma dicing. It also requires theadditional demand of aligning the backside mask with the front sidedevice pattern.

Therefore, what is needed is a plasma etching apparatus which can beused for dicing a semiconductor substrate into individual die and whichis compatible with the established wafer dicing technique of handling asubstrate mounted on support film and supported in a frame, and which isalso compatible with standard front side masking techniques.

Nothing in the prior art provides the benefits attendant with thepresent invention. Therefore, it is an object of the present inventionto provide an improvement which overcomes the inadequacies of the priorart devices and which is a significant contribution to the advancementto the dicing of semiconductor substrates using a plasma etchingapparatus.

Another object of the present invention is to provide a method fordicing a substrate on a composite film, the method comprising providinga work piece having a support film, a frame and a substrate, thesubstrate having a top surface and a bottom surface, the top surface ofthe substrate having at least one die region and at least one streetregion; providing the composite film interposed between the substrateand the support film; etching substrate material from the at least onestreet region to expose a portion of the composite film using asubstrate etch process; etching a first component of the composite filmusing a first etch process; and plasma etching a second component of theexposed portion of the composite film using a second etch process.

Yet another object of the present invention is to provide a method fordicing a substrate on a die attach film, the method comprising providinga work piece having a support film, a frame and a substrate, thesubstrate having a top surface and a bottom surface, the top surface ofthe substrate having at least one die region and at least one streetregion; providing the die attach film interposed between the substrateand the support film; etching substrate material from the at least onestreet region to expose a portion of the die attach film using asubstrate etch process; etching a first component of the die attach filmusing a first etch process; and plasma etching a second component of theexposed portion of the die attach film using a second etch process.

Still yet another object of the present invention is to provide a methodfor dicing a substrate on a die attach film, the method comprisingproviding a work piece having a support film, a frame and a substrate,the substrate having a top surface and a bottom surface, the top surfaceof the substrate having at least one die region and at least one streetregion; providing the die attach film interposed between the substrateand the support film; etching substrate material from the at least onestreet region to expose a portion of the die attach film using asubstrate etch process; isotropically etching a first component of thedie attach film using a first etch process; and anisotropically plasmaetching a second component of the exposed portion of the die attach filmusing a second etch process.

The foregoing has outlined some of the pertinent objects of the presentinvention. These objects should be construed to be merely illustrativeof some of the more prominent features and applications of the intendedinvention. Many other beneficial results can be attained by applying thedisclosed invention in a different manner or modifying the inventionwithin the scope of the disclosure. Accordingly, other objects and afuller understanding of the invention may be had by referring to thesummary of the invention and the detailed description of the preferredembodiment in addition to the scope of the invention defined by theclaims taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

The present invention describes a plasma processing apparatus whichallows for plasma dicing of a semiconductor substrate. After devicefabrication and any wafer thinning, the front side (circuit side) of thesubstrate can be masked using conventional masking techniques whichprotect the circuit components and leaves unprotected areas between thedie. The substrate is mounted on a thin support film which is supportedwithin a rigid frame. The substrate/support film/frame assembly istransferred into a vacuum processing chamber and exposed to reactive gasplasma where the unprotected areas between the die are etched away.During this process, the frame and support film are protected fromdamage by the reactive gas plasma. The processing can leave the diecompletely separated. After etching, the substrate/support film/frameassembly can be additionally exposed to plasma which removes potentiallydamaging residues from the substrate surface. After transfer of thesubstrate/support film/frame assembly out of the process chamber, thedie are removed from the support film using well known techniques andare then further processed (e.g., packaged) as necessary.

Another feature of the present invention is to provide a method fordicing a substrate on a composite film. The method comprising providinga work piece having a support film, a frame and a substrate. Thesubstrate has a top surface and a bottom surface. The top surface of thesubstrate has at least one die region and at least one street region.The composite film is interposed between the substrate and the supportfilm. Substrate material is etched from the at least one street regionto expose a portion of the composite film using a substrate etchprocess. A first component of the composite film is etched using a firstetch process. A second component of the exposed portion of the compositefilm is plasma etched using a second etch process. The composite filmcan contain matrix-based materials. The first component can be areinforcement component. The second component can be a matrix component.The first etch process can be at least partially isotropic. The firstetch process can be isotropic. The first etch process can have adifferent process chemistry than the second etch process. The secondetch process can be at least partially anisotropic. The second etchprocess can be anisotropic. The etching of the substrate material can bein a vacuum chamber and the etching of composite film can be in a vacuumchamber. The substrate can have a semiconducting layer such as Siliconand/or the substrate can have a layer such as GaAs. The substrate canhave a protective layer such as a photoresist layer that is patterned ona circuit side of the substrate. The substrate can be placed in aprocess chamber on a work piece support. A plasma source can be incommunication with the process chamber. The plasma source can be a highdensity plasma source. An electrostatic chuck can be incorporated intothe work piece support. The electrostatic chuck can clamp the work pieceto the work piece support. A thermal communication between the workpiece and the work piece support can be provided by supplying apressurized gas such as helium from the work piece support to the workpiece. The pressure within the process chamber can be reduced through avacuum pump and a process gas can be introduced into the process chamberthrough a gas inlet. A vacuum compatible transfer module can be providedthat communicates with the process chamber. The work piece can be loadedonto a transfer arm in the vacuum compatible transfer module whereby theprocess chamber is maintained under vacuum during a transfer of the workpiece from the vacuum compatible transfer module to the process chamber.

Yet another feature of the present invention is to provide a method fordicing a substrate on a die attach film. The method comprising providinga work piece having a support film, a frame and a substrate. Thesubstrate has a top surface and a bottom surface. The top surface of thesubstrate has at least one die region and at least one street region.The die attach film is interposed between the substrate and the supportfilm. Substrate material is etched from the at least one street regionto expose a portion of the die attach film using a substrate etchprocess. A first component of the die attach film is etched using afirst etch process. A second component of the exposed portion of the dieattach film is plasma etched using a second etch process. The first etchprocess can be at least partially isotropic. The first etch process canbe isotropic. The first etch process can have a different processchemistry than the second etch process. The second etch process can beat least partially anisotropic. The second etch process can beanisotropic. The substrate can contain a semiconducting layer such asSilicon and/or the substrate can contain a layer such as GaAs. Thesemiconducting layer is typically on the front side (e.g., circuit side)of the substrate. The substrate can have a protective layer such as aphotoresist layer that is patterned on a circuit side of the substrate.The substrate can be placed in a process chamber on a work piecesupport. A plasma source can be in communication with the processchamber. The plasma source can be a high density plasma source. Anelectrostatic chuck can be incorporated into the work piece support. Theelectrostatic chuck can clamp the work piece to the work piece support.A thermal communication between the work piece and the work piecesupport can be provided by supplying a pressurized gas such as heliumfrom the work piece support to the work piece. The pressure within theprocess chamber can be reduced through a vacuum pump and a process gascan be introduced into the process chamber through a gas inlet. A vacuumcompatible transfer module can be provided that communicates with theprocess chamber. The work piece can be loaded onto a transfer arm in thevacuum compatible transfer module whereby the process chamber ismaintained under vacuum during a transfer of the work piece from thevacuum compatible transfer module to the process chamber.

Still yet another feature of the present invention is to provide amethod for dicing a substrate on a die attach film. The methodcomprising providing a work piece having a support film, a frame and asubstrate. The substrate has a top surface and a bottom surface. The topsurface of the substrate has at least one die region and at least onestreet region. The die attach film is interposed between the substrateand the support film. Substrate material is etched from the at least onestreet region to expose a portion of the die attach film using asubstrate etch process. A first component of the die attach film isisotropically etched using a first etch process. A second component ofthe exposed portion of the die attach film is anisotropically plasmaetched using a second etch process. The method can further compriseremoving a portion of the die attach film during the step of etchingsubstrate material from the at least one street region. The first etchprocess can use at least one different process gas than the second etchprocess. The first etch process can use different process gases than thesecond etch process. The substrate can contain a semiconducting layersuch as Silicon and/or the substrate can contain a layer such as GaAs.The substrate can have a protective layer such as a photoresist layerthat is patterned on a circuit side of the substrate. The substrate canbe placed in a process chamber on a work piece support. A plasma sourcecan be in communication with the process chamber. The plasma source canbe a high density plasma source. An electrostatic chuck can beincorporated into the work piece support. The electrostatic chuck canclamp the work piece to the work piece support. A thermal communicationbetween the work piece and the work piece support can be provided bysupplying a pressurized gas such as helium from the work piece supportto the work piece. The pressure within the process chamber can bereduced through a vacuum pump and a process gas can be introduced intothe process chamber through a gas inlet. A vacuum compatible transfermodule can be provided that communicates with the process chamber. Thework piece can be loaded onto a transfer arm in the vacuum compatibletransfer module whereby the process chamber is maintained under vacuumduring a transfer of the work piece from the vacuum compatible transfermodule to the process chamber.

The foregoing has outlined rather broadly the more pertinent andimportant features of the present invention in order that the detaileddescription of the invention that follows may be better understood sothat the present contribution to the art can be more fully appreciated.Additional features of the invention will be described hereinafter whichform the subject of the claims of the invention. It should beappreciated by those skilled in the art that the conception and thespecific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top down view of a semiconductor substrate illustratingindividual devices separated by streets;

FIG. 2 is a cross-sectional view of a semiconductor substrateillustrating individual devices separated by streets;

FIG. 3 is a cross-sectional view of a semiconductor substrate mounted tosupport film and a frame;

FIG. 4 is a cross-sectional view of a semiconductor substrate mounted tosupport film and a frame being etched by a process;

FIG. 5 is a cross-sectional view of separated semiconductor devicesmounted to support film and a frame;

FIG. 6 is a cross-sectional view of a vacuum processing chamber;

FIG. 7 is a cross-sectional of a wafer/frame in process position;

FIG. 8 is a cross-sectional view of a semiconductor substrate mounted tosupport film and a frame supported by a transfer arm;

FIG. 9 is a cross-sectional view of a wafer/frame in a transferposition;

FIG. 10 is a schematic view of a work piece according to one embodimentof the present invention;

FIG. 11A is a schematic view of a work piece where substrate materialhas been removed in a street region;

FIG. 11B is a schematic view of a point in the dicing process flow wherethe composite film has been at least partially removed in the streetregions;

FIG. 12A is a flow chart of a portion of an improved substrate dicingsequence according to one embodiment of the present invention;

FIG. 12B is a flow chart of a portion of an improved substrate dicingsequence according to one embodiment of the present invention;

FIG. 13A is a flow chart of a portion of an improved substrate dicingsequence according to one embodiment of the present invention;

FIG. 13B is a flow chart of a portion of an improved substrate dicingsequence according to one embodiment of the present invention;

FIG. 14A is a schematic view of a work piece where the substratematerial has been removed in the street regions;

FIG. 14B is a schematic view of a work piece after a first process hasbeen performed to remove the first component of the composite film;

FIG. 14C is a schematic view of a work piece after the second processhas been performed to remove a second component of the composite film;

FIG. 15 is a flow chart of a portion of an improved substrate dicingsequence according to one embodiment of the present invention;

FIG. 16A is a schematic view of a work piece after substrate material ina street region has been removed;

FIG. 16B is a schematic view of a barrier film that has been applied toprotect the device;

FIG. 16C is a schematic view of a portion of the work piece where thebarrier film has been removed from a portion of the street region,exposing the composite film;

FIG. 16D is a schematic view of a work piece after a first process hasbeen performed to remove a first component of the composite film;

FIG. 16E is a schematic view of a portion of the work piece where thesecond component of a composite film has been removed with a secondprocess; and

FIG. 16F is a schematic view of a portion of the work piece where thebarrier film has been removed.

Similar reference characters refer to similar parts throughout theseveral views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

A typical semiconductor substrate after device fabrication isillustrated in FIG. 1. The substrate (100) has on its surface a numberof areas containing device structures (110) separated by street areas(120) which allows for separation of the device structures intoindividual die. Although silicon is commonly used as a substratematerial, other materials chosen for their particular characteristicsare frequently employed. Such substrate materials include GalliumArsenide and other III-V materials or non-semi-conductor substrates onwhich a semi-conducting material has been deposited (e.g., a polymericsubstrate with a thin film semiconductor device fabricated on thepolymer). Further substrate types may also include Silicon-On-Insulator(SOI) wafers and semiconductor wafers mounted on carriers. While theexample above describes die separated by streets, aspects of theinvention may be beneficially applied to other pattern configurations ona substrate.

In the present invention, as is shown in a cross sectional view in FIG.2, the device structures (110) are then covered with a protectivematerial (200) while the street areas (120) remain unprotected. Thisprotective material (200) can be a photoresist, applied and patterned bywell-known techniques. Some devices, as a final process step are coatedwith a protective dielectric layer such as silicon dioxide or PSG whichcan be applied across the whole substrate. This can be selectivelyremoved from the street areas (120) by patterning with photoresist andetching the dielectric material, as is well known in the industry. Thisleaves the device structures (110) protected by the dielectric materialand the substrate (100) substantially unprotected in the street areas(120). Note that in some cases test features to check the wafer qualitymay be located in the street areas (120). Depending on the specificwafer fabrication process flow, these test features may or may not beprotected during the wafer dicing process. Although the device patternillustrated shows oblong die, this is not necessary, and the individualdevice structures (110) may be any other shape, such as hexagons, asbest suits the optimum utilization of the substrate (100). It isimportant to note that while the previous example considers dielectricmaterials as the protective film, that the invention may be practicedwith a wide range of protective films including semi-conductive andconductive protective films. Furthermore, the protective layer canconsist of multiple materials. It is also important to note that someportion of the protective film may be an integral part of the finaldevice structure. (e.g., a passivation dielectric, metal bonding pad,etc.). Furthermore, the present invention can also be beneficially usedwith bulk wafers without the necessity of having devices or devicestructures. One such example may be a semiconductor substrate (Silicon,III-V compounds, etc.), mounted on a carrier or not mounted, covered bya masking material defining the structures to be etched. The substratemay also contain at least one additional layer with different materialproperties, such as for example an insulating layer.

The substrate (100) may be thinned, typically by a grinding process,which reduces the substrate thickness to a thickness in the range of afew hundred microns to approximately 30 microns or less. As is shown inFIG. 3, the thinned substrate (100) is then adhered to a support film(300) which in turn is mounted in a rigid frame (310) to form a workpiece (320). The frame is typically metal or plastic, though other framematerials are possible. The support film (300) is typically made from acarbon-containing polymer material, and may additionally have a thinconductive layer applied to its surface. The support film (300) providessupport for the thinned substrate (100) which may otherwise be toofragile to handle without breakage. It should be noted that the sequenceof patterning, thinning and then mounting is not critical and the stepsmay be adjusted to best fit the particular devices and substrate and theprocessing equipment used. It is important to note that while theprevious example considers a work piece (320) that is comprised ofmounting a substrate (100) on an adhesive support film (300) which inturn is attached to a frame (310), that the invention is not limited bythe configuration of the wafer and carrier. The wafer carrier can becomprised a variety of materials. The carrier supports the substrateduring the plasma dicing process. Furthermore, the wafer need not beattached to the carrier using an adhesive—any method that holds thewafer to the carrier and allows a means thermal communication of thesubstrate to the cathode is sufficient (e.g., an electrostaticallyclamped carrier, a carrier with a mechanical clamping mechanism, etc.).

After mounting the substrate (100) with the support film (300) in thedicing frame (310), the work piece (320) is transferred into a vacuumprocessing chamber. Preferably, the transfer module is also under vacuumwhich allows the process chamber to remain at vacuum during transfer,reducing processing time and preventing exposure of the process chamberto atmosphere and possible contamination. As shown in FIG. 6, the vacuumprocessing chamber (600) is equipped with a gas inlet (610), a highdensity plasma source (620) to generate a high density plasma, such asan Inductively Coupled Plasma (ICP), a work piece support (630) tosupport the work piece (320), an RF power source (640) to couple RFpower to the work piece (320) through the work piece support (630) and avacuum pump (650) for pumping gas from the processing chamber (600).During processing, the unprotected areas (120) of substrate (100) can beetched away using a reactive plasma etch process (400) as shown in FIG.4. This can leave the devices (110) separated into individual die (500)as shown in FIG. 5. In another embodiment of the invention, theunprotected areas (120) of the substrate (100) are partially etched awayusing a reactive plasma etch process (400). In this case, a downstreamoperation, such as a mechanical breaking operation, can be used tocomplete the die separation. These downstream methods are well known inthe art.

While the previous example describes the invention using a vacuumchamber in conjunction with a high density plasma (e.g., ECRs, ICP,helicon, and magnetically enhanced plasma sources), it is also possibleto etch the unprotected areas of the substrate using a wide range ofplasma processes. For example, one skilled in the art can imaginevariations of the invention using a low density plasma source in avacuum chamber or even the use of plasmas at or near atmosphericpressures.

When the work piece (substrate/tape/frame assembly) (320) is in theposition for plasma processing, the frame (310) can be protected fromexposure to the plasma (400). Exposure to the plasma (400) may causeheating of the frame (310) which in turn may cause local heating of thesupport film (300). For commonly used dicing tapes, at temperaturesabove approximately 100° C., the physical properties of the support film(300) and its adhesive capability may deteriorate and it will no longeradhere to the frame (310). Additionally, exposure of the frame (310) tothe reactive plasma gas may cause degradation of the frame (310). Sincethe frame (310) is typically re-used after wafer dicing, this may limitthe useful lifetime of a frame (310). Exposure of the frame (310) to theplasma (400) may also adversely affect the etch process: for example theframe material may react with the process gas, effectively reducing itsconcentration in the plasma which may reduce the etch rate of thesubstrate material, thus increasing process time. To protect the frame(310), a protective cover ring (660), as shown in FIGS. 6 and 7, ispositioned above the frame (310). In one embodiment, the cover ring(660) does not touch the frame (310) since contact with the frame (310)(which would occur during transfer into the process chamber (600)) maygenerate undesirable particles.

The work piece (substrate/tape/frame assembly) (320) is transferred bothinto and out of the process chamber (600) by a transfer arm (1100) thatsupports the frame (310) and substrate (100). The transfer arm (1100)may support both the support film (300) and the frame (310) or the frame(310) alone, but it is important that the assembly (320) not besupported beneath the substrate (100) area alone because of the fragilenature of thinned substrates (100). The transfer arm (1100) has analignment fixture (1110) attached to it that aligns the frame (310) in arepeatable position before being transferred into the process chamber(600). The frame (310) can also be aligned by other techniqueswell-known in semiconductor processing (e.g., optical alignment). Thealignment can also be performed on the substrate (100) by suchwell-known techniques. It is important that the work piece(substrate/tape/frame assembly) (320) be aligned before placement withinthe process chamber (600) to avoid miss-processing as explained below.

When the work piece (e.g., substrate/tape/frame assembly) (320) istransferred into the process chamber (600), it is placed onto thelifting mechanism (680) and removed from the transfer arm (1100). Thereverse process occurs during transfer of the work piece (e.g.,substrate/tape/frame assembly) (320) out of the process chamber (600).The lifting mechanism (680) touches the frame (310) area and provides nopoint contact to the substrate (100). Point contact to the work pieceoverlapping the substrate (100) can cause damage to the substrate (100),particularly after die separation and unloading of the work piece (320),since the flexibility of the support film (300) may cause the die tocontact each other and damage to occur. FIG. 9 shows the liftingmechanism (680) lifting the frame (310) from the underside; however, theframe (310) can also be removed from the transfer arm (1100) by contactwith the top surface, bottom surface, outer diameter of the frame (310)or any combination of these using a clamping device. In order to haveenough clearance to place the work piece (320) on the work piece support(630) to process the substrate (100), the frame (310), the work piecesupport (630), and the cover ring (660) can move relative to each other.This can be accomplished by moving the cover ring (660), the work piecesupport (630), or the lifting mechanism (680) or any combination of thethree.

During plasma processing, heat is transferred to all of the surfaces theplasma contacts including the substrate (100), support film (300), andframe (310). The cover ring (660) will minimize the heat transfer toareas of the support film (300) and the frame (310), but the substrate(100) must be exposed to the plasma (400) for processing.

As shown in FIG. 6, a perforated mechanical partition (690) may beinterposed between the plasma source (620) and the work piece support(630). The mechanical partition (690) can be electrically conductive(e.g., made from metal or metal coated). The mechanical partition (690)can be made of Aluminum. The mechanical partition (690) can help reducethe ion density as well as the plasma emission intensity reaching thework piece, while allowing a high level of neutral species to reach thework piece. The present invention offers control over the ion densityand plasma emission intensity reaching the work piece. It is preferredfor applications relevant to this invention, that the ion density andplasma emission intensity from the plasma source (620) reaching the workpiece be attenuated in the range of 10% to greater than 99 % by themechanical partition. In one preferred embodiment, the attenuation bythe mechanical partition can be greater than 10%. In one preferredembodiment, the attenuation by the mechanical partition can be greaterthan 30%. In yet another preferred embodiment, the attenuation by themechanical partition can be greater than 50 %. In yet another preferredembodiment, the attenuation by the mechanical partition is greater than90 %.

While the schematic in FIG. 6 shows a process chamber (600) with onemechanical partition (690), it may be beneficial to have more than onemechanical partition (690) disposed between the plasma source (620) andthe substrate (100). The mechanical partitions (690) can be the samesize and shape, or can be different sizes and/or shapes. The multiplemechanical partitions (690) may be configured in the same plane ordifferent planes (e.g., overlapped or stacked partitions). The multiplemechanical partitions (690) may have perforation shapes, sizes andpatterns that are identical or different from one another.

The substrate can be processed using techniques well known in thesemiconductor industry. Silicon substrates are generally processed usinga Fluorine based chemistry, such as SF₆. SF₆/O₂ chemistry is commonlyused to etch Silicon because of its high rate and anisotropic profile. Adisadvantage of this chemistry is its relatively low selectivity tomasking material for example to photoresist which is 15-20:1.Alternatively, a Timed Division Multiplex (TDM) process can be usedwhich alternates between deposition and etching to produce highlyanisotropic deep profiles. For example, an alternating process to etchSilicon uses a C₄F₈ step to deposit polymer on all exposed surfaces ofthe Silicon substrate (i.e., mask surface, etch sidewalls and etchfloor) and then an SF₆ step is used to selectively remove the polymerfrom the etch floor and then isotropically etch a small amount ofsilicon. The steps can repeat until terminated. Such a TDM process canproduce anisotropic features deep into Silicon with selectivities to themasking layer of greater than 200:1. This then makes a TDM process thedesired approach for plasma separation of Silicon substrates. Note thatthe invention is not limited to the use of fluorine containingchemistries or a time division multiplex (TDM) process. For example,silicon substrates may also be etched with Cl, HBr or I-containingchemistries as is known in the art.

For III-V substrates such as GaAs, a Chlorine based chemistry isextensively used in the semiconductor industry. In the fabrication ofRF-wireless devices, thinned GaAs substrates are mounted with the deviceside down onto a carrier, where they are then thinned and patterned withphotoresist. The GaAs is etched away to expose electrical contacts tothe front side circuitry. This well-known process can also be used toseparate the devices by the front side processing described in the abovementioned invention. Other semiconductor substrates and appropriateplasma processes can also be used for the separation of die in the abovementioned invention.

While the above examples discuss the use of plasma for separating die(dicing), aspects of the invention may be useful for relatedapplications such as substrate thinning by plasma etching. In thisapplication the substrate (100) can be have some features on the surfaceto be etched or alternatively the surface to be etched may befeatureless (e.g., thinning the bulk substrate).

Plasma dicing can efficiently singulate a wide ranges of devices. Somedie structures however contain at least one composite layer that can bedifficult to plasma etch without harming (e.g., damaging) the device. Anexample of such a structure would be a silicon device to be singulatedthat contains a die attach film (DAF). Die attach films are adhesivelayers that can be used to bond chips to one another. The die can besingulated prior to the bonding operation. During integrated circuitdevice fabrication, DAF can be used to create multi-chip stackedpackages.

In order to get the required mechanical and electrical film properties,die attach films (DAF) are often designed using composite materials. Forexample, a die attach film can consist of a polymeric matrix (e.g.,epoxy resins, etc.) with embedded filler materials (e.g., SiO₂particles, etc.). Both materials in this example (epoxy and SiO₂) arecapable of being plasma etched. For example, the polymer matrix can beetched in an oxygen containing plasma. A silicon dioxide (SiO₂)component can also be plasma etched, though due to the strength of thesilicon to oxygen bond, ion energy or higher wafer temperatures areoften required to get a commercially viable SiO₂ plasma etch rate. Whilethese higher ion energy and/or higher temperature conditions will etchan SiO₂ component in a DAF film, these conditions will also typicallyetch exposed materials of the device structure, potentially damaging thedevice (e.g., degrading device performance and/or yield). Thereforethere is a need to be able to remove composite materials during a dicingprocess flow that does not significantly damage the singulated devices.

FIG. 10 shows an example of a work piece (2800). The work piece (2800)is similar to work piece (320) with the addition of at least onecomposite layer (2810) to be singulated. The work piece can contain asubstrate (100) that contains at least one device structure (110) and atleast one street region (120). The device structure (110) can be atleast partially covered by a protective film (200).

In all embodiments, the composite layer (2810) can be composed of morethan one component. The components of the composite film can differ fromone another by chemical property (e.g., composition) or physicalproperty (e.g., material phase, material structure, etc.) or both. Thecomposite layer (2810) can be less than 100 microns thick. The compositelayer (2810) can be less than 50 microns thick. The composite layer(2810) can be less than 25 microns thick

In all embodiments, a composite material can contain carbon (e.g.,polymeric materials, graphite, SiC, etc.). A composite material cancontain silicon (e.g., Si, SiO₂, SiC, SiN, etc.). A composite materialcan contain a metal.

In all embodiments, a composite layer can be in contact with thesubstrate (100). A composite layer can be in contact with the supportfilm (300). A composite material can be in contact with both thesubstrate (100) and the support film (300). A composite film can beadhesively attached to the substrate (100). The composite layer (2810)can be interposed between the substrate (100) and the support film. Acomposite layer can be a die attach film (DAF). The composite film canbe a DAF that contains a filler material. The DAF filler material cancontain Si. The DAF filler material can be SiO₂.

The composite layer can contain a material that requires an ion-assistedplasma etch mechanism to etch in a plasma. The composite layer cancontain a material that is permeable to vapor hydrogen fluoride.

A composite material can contain a matrix component. The matrixcomponent can contain a metal. The matrix component can contain carbon(e.g., polymer, etc.) The matrix component can be a polymeric matrix.The polymer matrix can be a thermoset. The polymer matrix can be athermoplastic. The polymeric matrix can contain any of the followingresins: epoxy, polyimide, polyamide, polyester, etc. The matrix cancontain more than one component (e.g., resin, copolymers, blendedpolymers, etc.). The matrix component can be carbon. The matrixcomponent can encapsulate a filler component.

The composite material can contain a composite reinforcement (e.g.,filler, etc.). The reinforcement material can comprise greater than 5%of the composite material. The reinforcement material can comprisegreater than 25% of the composite material. The reinforcement materialcan comprise greater than 50% of the composite material. Thereinforcement material can comprise greater than 75% of the compositematerial. The reinforcement material can comprise greater than 90% ofthe composite material. The reinforcement material can be in discretedomains within the composite material (e.g., filler particles). Thecomposite reinforcement can contain a wide range of materials includingcarbon-containing materials, silicon-containing materials,metal-containing materials, ceramic, etc. The composite reinforcementcan contain silicon dioxide (SiO₂). The composite reinforcement can haveisotropic or anisotropic composition. The composite material can be afiber reinforced composite. A fiber reinforced composite can containlong fibers, short fibers, or a combination of both. The compositematerial can be a flake reinforced composite. The composite material canbe a particle reinforced composite. The particle reinforced compositecan contain spherically shaped particles. The particles can be solid,hollow, or a combination of both. The composite material can be alaminar reinforced composite.

FIGS. 11A and 11B show the work piece (2800) at various stages in asingulation process.

FIG. 11A shows a work piece (2800) where substrate material (100) hasbeen removed in a street region (120). A substrate etch process can beused to remove substrate material from at least one street area (120).The substrate removal process can remove substrate material (100) fromsubstantially all street regions (120). The substrate removal processcan remove all substrate material from at least one street region. Thesubstrate removal process can remove substantially all substratematerial form substantially all street regions. During the substrateetch process, the work piece temperature is typically held below amaximum value that might damage the support film tape. Many supportfilms (e.g., dicing tapes) are compatible up to approximately 100° C.Some support films can be compatible to 200° C. and greater.

The substrate etch process can be a vacuum process. The substrate etchprocess can be a plasma etch process. The plasma etch process can be acyclical process (e.g., Bosch process, deep reactive ion etch (DRIE)process, time division multiplex (TDM) process, etc.). The substrateetch process can be at least partially anisotropic. The substrate etchprocess can be completely anisotropic.

The substrate etch process can expose at least a portion of a compositefilm (120) overlapped by a street region (120). The substrate etchprocess can expose all of the composite layer overlapped by a streetregion (120).

The substrate etch process can be designed to remove a portion ofsubstrate material overlapped by the protective material (200) (e.g.,the substrate etch feature profile can be re-entrant. In other words,the width of the substrate etch feature (e.g., dicing street in thesubstrate) created by the substrate etch can be narrower at thesubstrate surface that contains the device (110) compared the featurewidth at the opposing face of the substrate)

The substrate etch process can remove the substrate material faster thanthe composite material (e.g., the substrate etch process can have asubstrate:composite etch selectivity (rate of substrate removal/rate ofcomposite film removal) greater than one). The substrate etch processcan have a substrate:composite etch selectivity great than 10. Thesubstrate etch process can have a substrate:composite etch selectivitygreat than 100. The composite material can act as an etch stop for thesubstrate etch process.

The substrate etch process can etch the composite material. Thesubstrate can remove a portion of the composite material. The substrateremoval process by itself does not expose the support film in a streetregion where the composite film overlaps the street region. Thesubstrate etch process alone does not etch through the composite film.

FIG. 11B shows a point in the dicing process flow where the compositefilm (2810) has been at least partially removed in at least one streetregion (120). The composite film (2810) can be completely removed in atleast one street region (120). The composite layer (2810) can be damagedor removed in order to singulate the die. The composite film can becompletely removed in the street regions (120).

FIG. 12A is a flow chart of a portion of an improved substrate dicingsequence. Once the substrate material has been removed in at least onestreet region (120), the composite film needs to be processed tocontinue the singulation process. The composite film process can be anetch process. The composite film process can consist of multiple steps.

In order to process the composite film, the improved process can use afirst process to etch a first component of the composite film. The firstprocess can selectivity etch a first component of the composite film.The selectivity between two materials for a removal process is definedas the ratio of the process material removal rates of the two materials.The process selectivity for the first process (e.g., the removal rate offirst composite film component/removal rate of another composite filmcomponent (first component: another component)) can be greater than 1:1.The first component: another component selectivity for the first processcan be greater than 10:1. The first component: another componentselectivity for the first process can be greater than 100:1. The firstcomposite film component can be a reinforcement component.

The first process can remove material in a manner that is at leastpartially isotropic. The first removal process can be completelyisotropic.

The first process can remove a first composite film component from atleast a portion of the composite film. The first process can remove thefirst component from at least a portion of the composite film where thecomposite film is not overlapped by the substrate. The first process canremove at least a portion of the composite film overlapped by a streetregion. The first process can remove the first component of thecomposite film overlapped by a street region. The first process canremove all of the first component of the composite material in thecomposite material overlapped by street regions. The first process canremoval substantially all of the first composite component from at leasta portion of the composite film.

The first process can be selective to the substrate (e.g., removal rateof first composite film component/removal rate of the substrate (firstcomponent: substrate) is greater than 1:1). The first process firstcomponent: substrate selectivity can be greater than 10:1. The firstprocess first component: substrate selectivity can be greater than100:1.

The first process can be selective to the support film (e.g., removalrate of the first composite film component/removal rate of the supportfilm (first component: support film) is greater than 1:1). The firstprocess first component: support film selectivity can be greater than10:1. The first process first component: support film selectivity can begreater than 100:1.

The first process can be a vapor phase process. The first process can bea process that does not contain a plasma. The first process can includea fluorine-containing process gas. The fluorine-containing process gascan be hydrogen fluoride vapor (VHF). At least one reactant in the firstprocess can diffuse through a component of the composite material (e.g.,VHF can readily diffuse through some types of polymer layers). The firstprocess can be capable of removing a first composite material that isnot exposed (e.g., the first composite is embedded within the compositematerial - for example a VHF containing process for the removal of SiO₂within a SiO₂ reinforced composite with a polymeric matrix). It ispreferred that first composite material etch process does not damage thedevice. The first process can be a vacuum process. The pressure of thefirst process can be higher than the pressure in the substrate etchprocess.

Following a first process, a second process can be applied to thecomposite film. The second process can be an etch process. The secondprocess can be a plasma etch process. The second process can remove asecond component of the composite film. The second process canselectively remove a second component of the composite film. The secondprocess can remove at least a portion of the second component of thecomposite film. The second process can be a vacuum process. The secondprocess can be at a lower pressure than the first process.

The second process can employ a different process chemistry from thefirst process. The second process can contain at least one differentprocess gas than the first process. The second process can contain morethan one different process gas than the first process. The secondprocess may have no common process gases with the first process. Thesecond process can utilize an oxygen containing reactant (e.g., O₂, O₃,CO₂, CO, SO₂, etc.). The second process can utilize a nitrogencontaining reactant (e.g., N₂, N₂O, C_(x)H_(y)OH, etc.). The secondprocess can utilize a hydrogen containing reactant (e.g., H₂, NH₃, H₂O,etc.).

In embodiments containing a work piece (2800), the process selectivityfor the second process (e.g., the removal rate of second composite filmcomponent/removal rate of another composite film component (secondcomponent: another component)) can be greater than 1:1. The secondcomponent: another component selectivity for the second process can begreater than 10:1. The second component: another component selectivityfor the second process can be greater than 100:1. The second compositefilm component can be a matrix component.

The second process can remove material in a manner that is at leastpartially anisotropic. The second process can be completely anisotropic.The second process can be at least partially anisotropic. The secondprocess can remove the second component faster in the directionperpendicular to the plane of the support film than the directionparallel to the plane of the tape. The second process can be isotropic.

The second process can remove a second composite film component from atleast a portion of the composite film. The second process can remove thesecond component from at least a portion of the composite film where thecomposite film is not overlapped by the substrate. The second processcan remove at least a portion of the composite film overlapped by astreet region. The second process can remove the second component of thecomposite film overlapped by a street region. The second process canremove all of the second component of the composite material in thecomposite material overlapped by street regions. The second process canremoval substantially all of the second composite component from atleast a portion of the composite film.

The second process can be selective to the substrate (e.g., removal rateof second composite film component/removal rate of the substrate (secondcomponent: substrate) is greater than 1:1). The second process secondcomponent: substrate selectivity can be greater than 10:1. The secondprocess second component: substrate selectivity can be greater than100:1.

The second process can be non-selective to the support film (e.g.,removal rate of the second composite film component / removal rate ofthe support film (second component: support film) is less than or equalto 1:1). The second process does not etch completely through the supportfilm. The second process may etch into the support film. The secondprocess may etch into the support film in regions overlapped by at leastone street region. The second process may etch into the support film inall regions overlapped by all street regions. The second process mayetch less than 10 microns deep into the support film. The second processmay etch less than approximately 10 microns deep in regions overlappedby a street region. In the case where the second process is notcompletely isotropic, the second process may remove at least a portionof the second component in at least one region overlapped by thesubstrate.

FIG. 12B shows another embodiment of the invention. It is preferred thatthe first and second processes do not damage the device. FIG. 12Billustrates an embodiment of the invention where at least one of thecomposite material etch processes may cause damage to the device. Inthis embodiment, a barrier film can be applied to the device prior tothe composite film processing step. The barrier film can be appliedprior to the substrate etch process. The barrier film can be appliedprior to the substrate being assembled into a work piece. The barrierfilm can be applied after the substrate removal process. The barrierfilm protects the device from being degraded by at least one step of thecomposite film removal process. The barrier film can be applied by avacuum coating process. The barrier film can be silicon containing. Thebarrier film can be SiN. The barrier film can be a silicon rich SiNfilm. The barrier film can be silicon (e.g., amorphous Si, etc.). Thebarrier film can be carbon-containing. The barrier film can containorganic materials. The barrier film can contain polyimide. The barrierfilm can contain paralyne. The barrier film can be removed after thecomposite film removal process. After the substrate etch process hasbeen performed, a first process etches a first component of thecomposite film. After the first process has been performed, a secondprocess etches a second component of the composite film. After thesecond process has been performed, the work piece can be sent downstreamfor further processing.

FIG. 13A shows another embodiment of the invention. In this embodimentsubstrate is removed in at least one street region exposing a compositelayer. After the substrate etch process has been performed, a firstprocess etches a first component of the composite film. After the firstprocess has been performed, a second process etches a second componentof the composite film. After the second process has been performed, thework piece can be sent downstream for further processing.

FIG. 13B shows yet another embodiment of the invention. In thisembodiment, the substrate material is removed from at least one streetregion. After the substrate etch process has been performed, a firstprocess etches a first component of the composite film. After the firstprocess has been performed, a second process etches a second componentof the composite film.

Following the second process, if the composite layer is not sufficientlyprocessed, the first process and second process can be repeated. Thefirst process and second process can be repeated at least one time. Alooped process can contain one process step (e.g., a one-step loop thatis morphed or changed between at least one subsequent iteration throughthe step). A looped process can contain at least two process steps. Alooped process can execute at least one process step then repeats atleast one of the process steps. FIG. 13B shows an example of a loopedprocess. In a looped process, at least one process step can be repeatedmore than one time. If a process step is repeated in a looped process,the process conditions can be the identical to the previous iteration(or loop). The process conditions of at least one process step canchange between two repeated process loops. The repeated processconditions can change between more than two repeated process loops. Therepeated process conditions can change between every repeated processloop. The repeated process conditions of at least one process step canchange in every loop. FIGS. 14A-C illustrate the work piece conditionfor a portion of the inventive process. FIG. 14A shows a work piecewhere the substrate material has been removed in the street regions. Thecomposite layer (3205) has been exposed in the street regions. Thecomposite film in FIG. 14A consists of a first component (3220) and asecond component (3210). FIG. 14B shows the work piece after a firstprocess has been performed to remove the first component (3220) of thecomposite film (3205). The first component has been removed from thecomposite film (3205) in areas where the composite film overlaps thestreet region. The removal of the first component (3220) can leave avoid (3230) in the composite material (3210). FIG. 14C shows the workpiece after the second process has been performed to remove a secondcomponent (3210) of the composite film (3205). The second component hasbeen removed in areas where the composite film overlaps the streetregion. In FIG. 14C, the die has been singulated.

FIG. 15 shows another embodiment of the invention. In this embodiment, asubstrate removal process is performed to remove substrate material froma street region. After substrate material has been removed, a barrierlayer can be added to protect the device from damage from subsequentprocesses. It is important to note that the barrier film can be appliedprior to the substrate removal process. After the composite layer hasbeen exposed, a first process is performed to etch a first compositefilm component. A second process is performed to etch a second compositefilm component. The barrier layer on the device can be removed. The workpiece can sent downstream for additional processing.

FIGS. 16A-F show a section of the work piece for a process flowillustrated in FIG. 15. FIG. 16A shows the work piece after substratematerial in a street region has been removed. The composite film hasbeen exposed in a street region. FIG. 16B shows a barrier film has beenapplied to protect the device. The barrier film can coat the substratesurfaces exposed during the substrate removal process. The barrier filmcan coat the exposed surface of the composite film. Since the barrierfilm is designed to resist the composite film removal process, thebarrier film should be removed from the composite film in areas to beremoved. The barrier film can be removed from the street region. FIG.16C shows a portion of the work piece where the barrier film has beenremoved from a portion of the street region, exposing the compositefilm. FIG. 16D shows the work piece after a first process has beenperformed to remove a first component (3220) of the composite film(3420). The removal of the first component (3220) can leave a void(3230) in the composite film. FIG. 16E shows a portion of the work piecewhere the second component of a composite film has been removed with asecond process. The support film (300) has been exposed. FIG. 16F showsa portion of the work piece where the barrier film has been removed. Thedie (500) has been singulated at this point and can be sent down streamfor further processing.

In all embodiments, the substrate etch process and the first process canbe performed in the same process chamber. The first process and thesecond process can be performed in the same process chamber. Thesubstrate etch process and the second process can be performed in thesame chamber. The substrate etch process, the first process, and thesecond process can all be performed in the same chamber.

In cases where the substrate etch process and the first process are bothvacuum processes, both processes can be performed without exposing theworkpiece to atmosphere (e.g., a substrate etch process at vacuumfollowed by a first process at vacuum with any operations (e.g., wafertransport, etc.) between the substrate etch and first process also invacuum).

In cases where the substrate etch process and the second process areboth vacuum processes, both processes can be performed without exposingthe workpiece to atmosphere (e.g., a substrate etch process at vacuumfollowed by a second process at vacuum with any operations (e.g., wafertransport, etc.) between the substrate etch and first process also invacuum).

In cases where the first process and the second process are both vacuumprocesses, both processes can be performed without exposing theworkpiece to atmosphere (e.g., a first etch process at vacuum followedby a second process at vacuum with any operations (e.g., wafertransport, etc.) between the substrate etch and first process also invacuum).

In cases where the substrate etch, first process and the second processare all vacuum processes, the processes can all be performed withoutexposing the workpiece to atmosphere (e.g., a substrate etch, first etchprocess, and a second process at vacuum with any operations (e.g., wafertransport, etc.) between the processes also in vacuum).

By way of example, FIG. 16 illustrates the invention as applied to awork piece that contains a die attach film (DAF)—see FIG. 16A. The DAFfilm (3205), contains approximately 50% of an SiO₂ filler (3220) in anepoxy-containing polymer matrix (3210). The SiO₂ particles (3220) wereapproximately 1 micron in diameter. A plasma etch process using a deepreactive ion etch (DRIE) etch process was used to remove the substratematerial (not shown) from the street regions. The plasma etch processwas implemented on a commercially available MDS-100 plasma etch systemby Plasma-Therm, LLC and used three steps per loop as shown in the tablebelow:

Deposition Etch A Etch B Time <sec> 1-10  1-5  1-20  Pressure <mtorr>10-150  10-150  50-2000 SF₆ Flow <sccm> 0-100 0-300 200-2000  C₄F₈ Flow<sccm> 50-200  0-100 0-100 O₂ Flow <sccm> 0-100 0-100 0-500 Ar Flow<sccm> 0-200 0-200 0-200 RF Bias Power <W> 0-100  0-1000 0-200 ICP Power<W> 500-5000  500-5000  1000-10000+

For the example above, after the plasma etch removes the substratematerial in the street regions, the work piece is exposed to a firstprocess containing VHF to remove the SiO₂ filler from the composite DAFmaterial (3205). The VHF material readily removes the SiO₂ particles inthe exposed street regions by diffusing through the polymer matrix ofthe DAF. The VHF process removes the SiO₂ particles with minimal loss ofthe polymer matrix and the substrate. VHF processing for etching SiO₂sacrificial films is known in the art. An example of VHF processparameters is shown in the table below:

VHF Process Time <sec>  10-1200 Pressure <torr> 0.1-200  Temperature <°C.> −10-+100

For the example above, after the VHF removes the SiO₂ fillers from thecomposite DAF material, a single step plasma etch process is applied inorder to fully remove the polymer matrix. An example of this single stepplasma etch process is described in the table below:

Plasma Etch Time <sec> 60-1200 Pressure <mtorr> 10-150  O₂ Flow <sccm>0-200 Ar Flow <sccm> 0-200 RF Bias Power <W> 0-500 ICP Power <W>500-5000 

An example of a composite film process that might damage a device is theuse of a vapor hydrogen fluoride (VHF) process with a device thatcontains an SiO₂ layer. The VHF molecule will readily etch SiO₂ filmsand may degrade device performance. Even in the case where an SiO₂device layer is covered by an organic layer (e.g., resist, water solublepolymer, etc.), the organic layer may be permeable to VHF andconsequently not protect the SiO₂ layer from VHF etching. The VHFmolecule can diffuse through many organic (e.g., polymeric) films. Inthis case a barrier layer can provide the device protection from damagefrom the VHF etchant.

The present disclosure includes that contained in the appended claims,as well as that of the foregoing description. Although this inventionhas been described in its preferred form with a certain degree ofparticularity, it is understood that the present disclosure of thepreferred form has been made only by way of example and that numerouschanges in the details of construction and the combination andarrangement of parts may be resorted to without departing from thespirit and scope of the invention.

What is claimed is:
 1. A method for dicing a substrate on a compositefilm, the method comprising: providing a work piece having a supportfilm, a frame and a substrate, the substrate having a top surface and abottom surface, the top surface of the substrate having at least one dieregion and at least one street region; providing the composite filminterposed between the substrate and the support film; etching substratematerial from the at least one street region to expose a portion of thecomposite film using a substrate etch process; etching a first componentof the composite film using a first etch process; and etching a secondcomponent of the exposed portion of the composite film using a secondetch process.
 2. The method according to claim 1 wherein the compositefilm contains a matrix-based material.
 3. The method according to claim1 wherein the first component is a reinforcement component.
 4. Themethod according to claim 1 wherein the second component is a matrixcomponent.
 5. The method according to claim 1 wherein the first etchprocess is at least partially isotropic.
 6. The method according toclaim 1 wherein the first etch process is isotropic.
 7. The methodaccording to claim 1 wherein the first etch process having a differentprocess chemistry than the second etch process.
 8. The method accordingto claim 1 wherein the second etch process is at least partiallyanisotropic.
 9. The method according to claim 1 wherein the second etchprocess is anisotropic.
 10. The method according to claim 1 wherein theetching of the substrate material is in a vacuum chamber and the etchingof the composite film is in a vacuum chamber.
 11. A method for dicing asubstrate on a die attach film, the method comprising: providing a workpiece having a support film, a frame and a substrate, the substratehaving a top surface and a bottom surface, the top surface of thesubstrate having at least one die region and at least one street region;providing the die attach film interposed between the substrate and thesupport film; etching substrate material from the at least one streetregion to expose a portion of the die attach film using a substrate etchprocess; etching a first component of the die attach film using a firstetch process; and plasma etching a second component of the exposedportion of the die attach film using a second etch process.
 12. Themethod according to claim 11 wherein the first etch process is at leastpartially isotropic.
 13. The method according to claim 11 wherein thefirst etch process is isotropic.
 14. The method according to claim 11wherein the first etch process having a different process chemistry thanthe second etch process.
 15. The method according to claim 11 whereinthe second etch process is at least partially anisotropic.
 16. Themethod according to claim 11 wherein the second etch process isanisotropic.
 17. A method for dicing a substrate on a die attach film,the method comprising: providing a work piece having a support film, aframe and a substrate, the substrate having a top surface and a bottomsurface, the top surface of the substrate having at least one die regionand at least one street region; providing the die attach film interposedbetween the substrate and the support film; etching substrate materialfrom the at least one street region to expose a portion of the dieattach film using a substrate etch process; isotropically etching afirst component of the die attach film using a first etch process; andanisotropically plasma etching a second component of the exposed portionof the die attach film using a second etch process.
 18. The methodaccording to claim 17 further comprising removing a portion of the dieattach film during the step of etching substrate material from the atleast one street region.
 19. The method according to claim 17 whereinthe first etch process uses at least one different process gas than thesecond etch process.
 20. The method according to claim 17 wherein thefirst etch process uses different process gases than the second etchprocess.